COBOT: Conditional Ordinal-By-Ordinal Test

URL of this page: http://biostat.mc.vanderbilt.edu/OrdinalRegression

We developed a method for testing for association between two ordinal variables, Y and X, while adjusting for covariates Z. The data analysis program (COBOT-analysis.r) is written in R (www.r-project.org). The main analysis functions are COBOT.emp() and COBOT.scores() for calculating empirical and asymptotic p-values when proportional odds models are used to model P(Y|Z) and P(X|Z). Please see the beginning lines of the file for detailed descriptions.

Version history

12/06/2010: Old version did not work for ordinal variables with 3 levels. The new version should work.

12/04/2011: The R Design package has been replaced by R rms package. The code is updated to reflect the change.

07/23/2012: a bug fix in the ifelse() calls inside function COBOT.scores().

Simulation code and other simulation results

Our simulation code is in COBOT-simulation.r.

Other simulation results not included in the article: ordinal-otherresults.pdf

Contact and paper

For questions, please contact chun.li@vanderbilt.edu or bryan.shepherd@vanderbilt.edu .

The paper that describes the method is:

Li C, Shepherd BE (2010) Test of association between two ordinal variables while adjusting for covariates. Journal of the American Statistical Association 105:612-620